1. Field of the Invention
This invention relates to an apparatus for making an opening through the wall of a blood vessel such as a vein or artery and for inserting into such opening so made a cannula.
2. Description of the Prior Art
Reference is made to my recently issued U.S. Pat. No. 4,411,653, entitled "Cannula Introducer" for a description of the prior art known at the time of filing that application. U.S. Pat. No. 3,762,416 entitled "Artery Entry Tool"provides for a tool to make an incision into an artery wall but does not have a trigger and release mechanism for the cutting blade that works in a manner to provide the desired ease of operation.
My above-mentioned U.S. Pat. No. 4,411,653, provides a rod housing, a blade-carrying rod within the housing, and a cannula carried by the housing for insertion into the blood vessel after making a slit therein by the blade. A blade-carrying rod is operated by a trigger to extend the blade to a cutting position wherein it extends from the end of the rod housing and cannula; however, after the cutting procedure, the surgeon or operator must release the trigger to withdraw the blade. The trigger is still operatively connected to the blade and if it is inadvertently moved, the blade can be extended to damage the cannula and when the cannula is removed from the blade, the blade can injure the patient, the operator, and those in the vicinity thereof.